An experimental investigation on flow boiling heat transfer of R-600a in a horizontal small tube

The local heat transfer coefficient and flow pattern were studied experimentally during flow boiling of R-600a inside a horizontal small tube (inner diameter ID = 1.0 mm). The effects of heat flux, mass velocity and vapor quality have been investigated. The tests were conducted at heat fluxes from 5 to 60 kW m−2, mass velocity from 240 to 480 kg m−2 s−1 at 25 °C saturation temperature. Results show that flow patterns are related to the heat transfer coefficient. Convective boiling was found to be predominant during the tests. Nucleate boiling was predominant only in low vapor quality region. The resultant database was compared against predicting correlation available in literature for heat transfer coefficient. It was found that mass velocity have significant influence of heat transfer coefficients.